linux-kernel - Re: [PATCH] panic: Don't print redundant backtraces on oops

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Date:	Mon, 19 Dec 2011 15:09:15 +0100
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] panic: Don't print redundant backtraces on oops

Hello Andrew,

On Fri, 2011-12-16 at 16:52 -0800, Andrew Morton wrote:
> On Wed,  7 Dec 2011 16:36:43 -0800
> Andi Kleen <andi@...stfloor.org> wrote:

[snip]

> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -78,7 +78,8 @@ NORET_TYPE void panic(const char * fmt, ...)
> >  	va_end(args);
> >  	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
> >  #ifdef CONFIG_DEBUG_BUGVERBOSE
> > -	dump_stack();
> > +	if (!oops_in_progress)
> > +		dump_stack();
> >  #endif
> 
> This is kinda related to Michael's
> kdump-fix-crash_kexec-smp_send_stop-race-in-panic.patch, below.
> 
> afacit Michael's patch will prevent panic-within-panic, and it does
> this by accident becasue we never thought about it.  But it won't fix
> panic-within-other-oops.
> 
> Is there some clever way in which we can satisfy both requirements in
> one hit?

I think the two problems are not related. My problem was that only one
CPU should execute panic. Andi's problem is that one (or more oops)
messages are scrolled away by a subsequent panic.

But I am not sure if Andi's patch solves all his problems. What e.g.
about panic_on_oom? Don't we have the same problem here?

Michael

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